Patent Application
20100004494
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The present invention relates to a novel process for preparing C3˜C13 hydrocarbons from methane. This invention is an extension of application CN200410022850.8 and relates to the following research results in more depth and detail.
Natural gas is the most abundant hydrocarbon resource on earth besides coal, and is mainly composed of methane with a small amount of other compounds such as ethane, propane, steam, and carbon dioxide. Compared with coal, natural gas is a cleaner hydrocarbon resource because it can be directly used as fuel or chemical feedstock to produce other chemical products. Since most natural gas resources are often discovered in remote areas and natural gas is difficult to compress and transport, the cost to use natural gas is quite high. On the other hand, the high stability of C—H bonds of methane makes the chemical conversion difficult. In currently available technologies, natural gas is mostly used to make hydrogen or synthesis gas (H2+CO) (also referred to as “syngas”). With the hydrogen being used to produce ammonia, and the syngas converted to methanol. Although the Fischer-Tropsch method can convert natural gas into fuel oil through a syngas process, the cost is higher than that of original petroleum refining method. Therefore, natural gas is not widely used as a substitute for petroleum to produce fuel oil or other chemical monomers. A new process for converting methane into easily transported liquid petroleum or other synthesis intermediates is thus desired. Since the syngas route is not a cost-effective process, it has been suggested to produce higher value chemicals from light alkanes by selective oxidation processes. Except for a few successful examples such as preparing maleic anhydride by oxidation of n-butane, most cases of selective oxidation method of light alkanes, such as CH4, C2H6 and C3H8, did not achieve successful application in chemical industry because of low conversion rate, low selectivity, and difficulty to separate the products.
Another method involves converting methane into methanol [Roy A., Periana et al., Science, 280, 560(1998)] and acetic acid [Roy A. Periana, et al., Science, 301, 814(2003)]. In such process, SO2 was produced that could not be recovered, and concentrated sulphuric acid, which was used as reactant and solvent, was diluted after the reaction and could not be used continuously. This method has not been industrialized.
In the earlier paper [G. A. Olah et al. Hydrocarbon Chemistry(Wiley, New York,1995)], Olah reported the process to form CH3Br and HBr by reacting methane and Br2, then to hydrolyze CH3Br to provide methanol and dimethyl ether. This report did not suggest or disclose how to recycle HBr. The object of such process was not to synthesize hydrocarbons, and the reported single-pass conversion rate of methane was lower than 20%. The inventors of the present invention had also designed a process to convert alkane to methanol and dimethyl ether (Xiao Ping Zhou et al., Chem Commun. 2294(2003); Catalysis Today 98, 317(2004).; U.S. Pat. No. 6,486,368; U.S. Pat. No. 6,472,572; U.S. Pat. No. 6,465,696; U.S. Pat. No. 6,462,243). Such process, however, related to the use of Br2 and the extra step of regenerating Br2. As known, the utilization and storage of vast amount of Br2 is very dangerous.
In some embodiments of the invention, a process for preparing C3˜C13 hydrocarbons from methane, oxygen and HBr/H2O is provided including the steps of reacting methane with oxygen and HBr/H2O over a first catalyst in a first reactor to form CH3Br and CH2Br2; converting CH3Br and CH2Br2 into C3˜C13 hydrocarbons and HBr over a second catalyst in a second reactor; and recovering the HBr produced in the second reactor.
In the process of the present invention, methane is converted into alkyl bromides and then the alkyl bromides are further converted into corresponding products. Meanwhile, HBr is collected and directed into the first reactor for reuse. This process has wide application in preparing chemicals. Embodiments of the present inventive process are energy-saving. For example, when gasoline is prepared by the inventive process, the two exothermic reactions included in the inventive process can be carried out under atmospheric pressure. In embodiments of the inventive process, the raw materials for preparing alkyl bromides are O2, natural gas and HBr/H2O, in which HBr/H2O solution are used as bromine source instead of Br2, and the use of HBr/H2O offers a much safer solution to overall process because the reactions are strong exothermic, and H2O from HBr/H2O can carry significant heat away. Thus, the temperature of the catalytic bed can be easily controlled. In embodiments of the present invention, HBr is regenerated in the process of converting alkyl bromides into hydrocarbons. Embodiments of the present do not require a separate step to regenerate Br2.
One aim of some embodiments of the present invention is to efficiently convert methane of natural gas into liquid hydrocarbons or easily-liquefied hydrocarbons.
Embodiments of the inventive process include two reactions shown below.
HBr can be reused in the reaction A to complete one cycle.
The catalysts were prepared as follows: Silica (10 g, SBET=1.70 m2/g), RuCl3 solution (0.00080 g Ru/mL) and corresponding metal nitrates solution (0.10M) were mixed in a mole ratio of components of catalysts given in Table 1, stirred at ambient temperature for 0.5 h, dried at 110° C. for 4 h, and then calcined at 450° C. for 12 h.
The catalytic reaction was carried out in the quartz-tube reactor (i.d. 0.80 cm, length 60 cm) at the temperatures shown in Table 1, packed with 1.0000 g catalyst with both ends filled with quartz sand, with reactant flows: 5.0 mL/min of methane, 5.0 mL/min of oxygen, 4.0 mL (liquid)/h of 40 wt % HBr/H2O solution. The products were analyzed by a gas chromatography. Results are set forth in Table 1.
The catalysts were prepared as follows: Silica (10 g, SBET=0.50 m2/g), RuCl3 solution (0.00080 g Ru/mL), La(NO3)3 solution (0.01M), Ba(NO3)2 solution (0.10M), Ni(NO3)2 solution (0.10M) were mixed in a mole ratio of 2.5% La, 2.5% Ba, 0.5% Ni, 0.1% Ru and 94.4% SiO2. The mixture was stirred at ambient temperature for 0.5 h, dried at 110° C. for 4 h, and then calcined at 450° C. for 12 h to give the catalyst with composition as La2.5% Ba2.5% Ni0.5% Ru0.1%/SiO2.
The catalytic reaction was carried out in the quartz-tube reactor (i.d. 1.50 cm, length 60 cm) at 660° C., packed with 5.000 g catalyst with both ends filled with quartz sand, with reactant flows: 15.0 mL/min of methane, 5.0 mL/min of oxygen, 6.0 mL(liquid)/h of 40 wt % HBr/H2O solution. The products were analyzed by a gas chromatography. Methane conversion rate was 32.0%, and the selectivity of CH3Br, CH2Br2, CO and CO2 were 80.8%, 0.67%, 15.7% and 2.9%, respectively.
The catalysts C1-C14 of example 25-38 in Table 2 were prepared as follows: HZSM-5 (Si/Al=360, 283 m2/g), water and Zn(NO3)2.6H2O (or Mg(NO3)2.6H2O) were mixed in a ratio given in Table 2 and stirred and impregnated at ambient temperature for 12 h, dried at 120° C. for 4 h, and then calcined at 450° C. for 8 h. The catalyst was tabletted at 100 atm pressure, and then crushed and sieved to 40-60 mesh to the catalysts shown in Table 2.
The catalysts of example 25-38 were used to convert CH3Br into hydrocarbons. The reaction was carried out in the glass-tube reactor (i.d. 1.50 cm) with 8.0 g catalyst at 240° C., with a flow of 6.8 mL/min of CH3Br. The products were analyzed by a gas chromatography. The conversion rate of CH3Br and the selectivity of hydrocarbons are set forth in Table 3. Cn in Table 3 means the total amount of alkanes containing n carbons.
The catalysts C15-C29 of example 39-53 in Table 4 were prepared as follows: (Si/Al=360, 283 m2/g), water and corresponding salts were mixed in a ratio given in Table 4 and stirred and impregnated at ambient temperature for 12 h, dried at 120° C. for 4 h, and then calcined at 450° C. for 8 h. The catalyst was tabletted at 100 atm pressure, and then crushed and sieved to 40-60 mesh to the catalysts shown in Table 4.
The catalysts of example 39-53 were used to convert CH3Br into hydrocarbons. The reaction was carried out in the glass-tube reactor (i.d. 1.50 cm) with 8.0 g catalyst at 200-240° C., with a flow of 6.8 mL/min of CH3Br. The products were analyzed by a gas chromatography. The conversion rate of CH3Br and the selectivity of hydrocarbons are given in Table 5. Cn in Table 5 means the total amount of alkanes containing n carbons.
For preparing the catalyst, Silica (10 g, SBET=0.50 m2/g), RuCl3 solution (0.00080 g Ru/mL), La(NO3)3 solution (0.10 M), Ba(NO3)2 solution (0.10 M), Ni(NO3)2 solution (0.10 M) were mixed in a mole ratio of 2.5% La, 2.5% Ba, 0.5% Ni, 0.1% Ru and 94.4% SiO2. The result solution was stirred at ambient temperature for 0.5 h, dried at 110° C. for 4 h, and then calcined at 450° C. for 12 h to give the catalyst with component as La2.5% Ba2.5% Ni0.5% Ru0.1%/SiO2.
The catalytic reaction was carried out in the quartz-tube reactor (i.d. 1.50 cm, length 60 cm) at 660° C., packed with 5.000 g catalyst with both ends filled with quartz sand, with reactant flows: 15.0 mL/min of methane, 5.0 mL/min of oxygen, 6.0 mL(liquid)/h of 40 wt % HBr/H2O solution. The products were analyzed by a gas chromatography. Methane conversion rate was 32.0%, and the selectivities of CH3Br, CH2Br2, CO and CO2 were 80.8%, 0.67%, 15.7% and 2.9%, respectively. The composite undergone first step reaction was directly introduced into glass-tube reactor (i.d. 1.5 cm) at 240° C., which was packed with 8.0 g 14.0 wt % MgO/HZSM-5 catalyst. The final products were analyzed by a gas chromatography. The conversions rate of CH3Br and CH2Br2 were 100% through the second reactor and the products were hydrocarbons of C2˜C13. The similar result was achieved using 8.0 g 14.0 wt % ZnO/HZSM-5 as a substitute for the catalyst in the second reactor.
In another example, catalytic reaction was also carried out in the quartz-tube reactor (i.d. 1.50 cm, length 60 com) at 660° C., packed with 5.000 g catalyst, but with reactant flows: 20.0 mL/min of methane, 5.0 mL/min of oxygen, 6.0 mL(liquid)/h of 40 wt % HBr/H2O solution. The products were analyzed by a gas chromatography. Methane conversion rate was 26.7%, and the selectivities of CH3Br, CH2Br2, CO and CO2 were 82.2%, 3.3%, 11.9% and 2.6%, respectively. The composite undergone first step reaction was directly introduced into glass-tube reactor (i.d. 1.5 cm) at 240° C., which was packed with 8.0 g 14.0 wt % MgO/HZSM-5 catalyst. The final products were analyzed by a gas chromatography. The conversions rate of CH3Br and CH2Br2 were 100% through the second reactor and the products were hydrocarbons of C2˜C13.
CO is the main by-product in first step reaction and it is difficult to separate from CH4. So CO and CH4 were returned into first reactor for further reaction without separation. CH4, O2, CO (N2 as internal standard) and 40 wt % HBr/H2O (6.0 mL/h) were fed together into the first reactor, with flows: 15.0 mL/min of CH4, 5.0 mL/min of O2, 3.0 mL/min of CO, 5.0 mL/min of N2, 6.0 mL/h of 40 wt % HBr/H2O (liquid). The reaction was carried out at 660° C. and the conversion rate of methane was 30.4%, the selectivities of CH3Br, CH3Br2 and CO2 were 86.5%, 1.7% and 11.8%, respectively. The total selectivity of CH3Br and CH3Br2 was 88.2%. The composite through first reaction was directly introduced into the second reactor in which CH3Br and CH3Br2 were all converted into hydrocarbons of C2˜C13.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200610031377.9 | Mar 2006 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN07/00780 | 3/12/2007 | WO | 00 | 8/7/2009 |
